Aeolian sand transport: Scaling of mean saltation length and height and implications for mass flux scaling

Abstract

Wind tunnel measurements of the mean saltation length $L$ and of different proxies of the mean saltation height $H$ in saturated aeolian sand transport indicate that $L$ and $H$ are relatively insensitive to both the wind speed and grain diameter $d$. The latter result is currently unexplained and contradicts the theoretical prediction $L\propto H\propto d$. This prediction is based on the assumption that the characteristic velocity $\sqrt{\tilde{g}d}$ of bed grains ejected by the splash of an impacting grain controls the average saltation kinematics. Here, we show that a recent analytical saltation model that considers only rebounds of saltating grains, but neglects splash ejection, is consistent with the measurements. The model suggests that the buffer layer of the inner turbulent boundary layer, which connects the viscous sublayer with the log-layer, is partially responsible for the insensitivity of $L$ and $H$ to $d$. In combination, the measurements and model therefore indicate that splash ejection, though important to sustain saltation, does not significantly affect the average saltation kinematics. This finding represents a strong argument against the Ungar and Haff (1987)-scaling and in favor of the Durán et al. (2011)-scaling of the saturated saltation mass flux, with implications for ripple formation on Mars. Furthermore, it supports the recent controversial claim that this flux is insensitive to soil cohesion.

References in corpus (4)

• A scaling law for aeolian dunes on Mars, Venus, Earth, and for subaqueous ripples
• The physics of sediment transport initiation, cessation, and entrainment across aeolian and fluvial environments
• Direct numerical simulations of aeolian sand ripples
• A lower-than-expected saltation threshold at Martian pressure and below

Cited by in corpus (4)

• Megaripple mechanics: bimodal transport ingrained in bimodal sands
• Aerodynamic roughness of rippled beds under active saltation at Earth-to-Mars atmospheric pressures
• The role of energetic flow structures on the aeolian transport of sediment and plastic debris
• Quantifying the form-flow-saltation dynamics of aeolian sand ripples